Thermostatic switch



May 15.1936. ESMITH 2,041,304

THERMOSTATIC SWITCH 4 Filed May 28, 195o 2 sheets-sheet i U1.. --1 I y.i Jf/gd "l 70] w |i1; l ml t :1 fun l l l lf3/1% K i 7 96 0J 20 /5 5u?, mi

10@ m it M M0 l' L x 1 "l, /7

,' ,/J "7 O /6 a /04 a fa@ /METHI- 25 502' EE r l" T INVENToR.

ATTORNE May 19, 1,936. J. E. SMITH 2,041,304

` THERMOSTATIC SWITCH A l Filed May 28, 193.0 2 Sheets-Sheet 2 CilPatented Mey 19, 1936 2,041,304 THERMosTATIc SWITCH John E. smith,Plainfield, N. J., assigner to Knapp-Monarch Company, a. corporation ofMissouri Application May 28, 1930, Serial No. 456,694

4 Claims.A (Cl. 200-116) My invention relates to electric switches and yhas for an object to provide a switch with thermostatic means forcontrolling the same.

A more specic object of the invention is to pro'- vide ay switch withactuating means for throwing the switch and a thermostat for controllingthe actuating means.

Another object of the invention is to provide a manually operable switchwith an auxiliary thermostatic actuating means, and a thermostatic pilotswitch for controlling the thermostatic actuating means.

Another object of my invention is to provide means for controlling acomparatively heav'y current with a delicate thermostatic switch, theparts being so arranged that the current will bc cut off on closure ofthe thermostatic switch so that there will be no current to be brokenwhen the thermostatic switch is opened and sparking at the contactpoints thereof will be avoided.

My invention is particularly adapted foruseI in controlling the supplyof current to a main electric resistance unit and a specific object ofthe invention is to provide a main switch in the circuit of saidresistance unit, means for actuating the switch, said means comprising athermostat and a local resistance for heating the same, said localresistance being controlled by the main switch and also by athermostatic pilot switch so that the local resista-nce is inactiveuntil the pilot switch is actuated by heat from the main electricresistance and then cuts off its own supply of current when it causesthe main switch to open. It will be evident that in such an arrangementthe pilot switch will not open until after the current has been cut oifby the main switch. l

Another object of the invention is to provide a local resistance of suchcapacity as to provide a predetermined time interval between theoperation of the pilot switch and the operation of the main switch.

Another object of the invention is to provide a switch and actuatortherefor which is incorporated in a plug connector so that it may bereadily applied to different apparatus.

Other objects will appear in the following description of a preferredembodiment of my invention and of certain modifications thereof andthereafter the novelty and scope of the invention will be pointed out inthe claims.

In the accompanying drawings;

Figure 1 is a view in front elevation of a coffee percolator partlybroken away and partly in sec'- tion showing my automatic switchmechanism applied thereto;

Fig. 2 is a fragmentary bottom plan-view of the same;

Fig. 3 is a detail view of the main switch and 5 thermostatic actuatortherefor;

Fig. 4 is a diagram of electrical connections used in the arrangementshown in Figs. 1 and 2;

Fig. 5 is a fragmentary view of an electric at iron showing another formof my invention 10 wherein the main switch and actuator are incorporatedin a switch plug;

Fig. 6 is a view mainly in longitudinal section but on a much largerscale of the switch plug shown in Fig. 5-; l5

Fig. 7 is a diagram of electrical connections employed in the embodimentshown in Figs. 5 and 6;

Fig. 8 is a side elevation partly in section of a wallie iron equippedwith my automatic switch mechanlsm;

Fig. 9 is a View partly in perspective and partly diagrammatic of myinvention as applied to a I mercury switch; and

Figs. 10 and 11 are views mainly in longitu- 25 dinal sectionillustrating my invention embodied in a connection plug wherein amercury switch is employed, Fig. 10 showing a plug adapted to be used inhorizontal position, and Fig. 11 a plug adapted to be used in verticalposition. 30

In Fig. 1, I have illustrated my invention as applied to a coffeepercolator of standard type comprising a receptacle l5 supported on ahollow base I6 and separated therefrom by a diaphragm I1. An electricresistance unit I 8 projects through the diaphragm into a pump chamberI9 in the receptacle. Water entering said chamber from the receptacle I5is locally heated by the resistance unit and steam bubbles are formedwhich cause the water to spurt up a central tube 20 and overowinto aperforated container or basket 2|. The-water then percolates through theground coffee in said basket and drops back into the main receptacle.The percolating starts before the main body of water in the receptacleis materially heated and will continue as long as current is supplied tothe heating unit. The strength of thecoiee extract depends upon thelength of time the current is kept on and it is desirable to turn offthe current automatically when a predetermined strength of extract isobtained. The temperature of the main body of liquid in the receptacleprovides a gage to determine when the current should be cut oi and Iemploy the heat of said liquid to initiate the opening of the cir cuitof the main resistance unit, as will be dey scribed hereinafter. i

A toggle switch of standard type is housed in a casing mounted lwithinthe hollow base I6. This switch has a handle 25 projecting outward fromthe base. The exact construction of the switch is immaterial to myinvention but it is de sirable that it be a snap switch. Eunice it tostate that in addition to the switch handle, l1 provide a link 21 forthrowing the switch. This link projects laterally from the casing 25 andwithin the hollow base I6 and is connected to the switch handle. Whenthe switch is closed by operating the handle 25, the link 21 isretracted and by pulling said link the switch may be opened and thehandle swung to of' position.

The switch casing 25 is supported on a bracket and secured to thisbracket is a comparatively powerful thermostat 3l in the iorm of a barmade up of a plurality of bimetallic laminae. The bar is xed at one endto the bracket 3D and the other end is formed with an aperture through'which passes a rod 32. One end of the rod is bent to form a head whichnormally engages the outer face of the thermostat (see Fig. 2), whilethe other end is connected to one corner of a triangular plate or lever34. Another corner of said lever is connected to the link 21 and thelever is fulcrumed at its third corner to the switch casing 25. Theparts are so proportioned that when the switch handle is turned to onposition, the thermostatic bar 3l will be flexed as shown in Fig. 3, bythe retraction ci! the link 21. When the bar is heated it will tend tostraighten and when its temperature is raised to a predetermined degreeit will develop power suilicient to rock the lever 34 on its fulcrum,pulling the link 21 and throwing the link to off position. To

avoid confusion', I shall hereafter call the thermostatic element 3| anactuator, so as to distinguish from another thermostat presently to be Ydescribed. In order to heat the actuator, I wrap a. coil 35 ofresistance wire thereabout said actuator.

In the circuit of the heating coil 35, I provide a thermostatic switchwhich I shall hereafter call the pilot switch. This pilot switchcomprises a bimetallic switch arm 3B secured to the outer face of thediaphragm I1. This switch arm will thus be 'exed by heat from thereceptacle I 5. The free end of the switch arm carries an electriccontact point 31 which is adapted to engage an opposed contact point 38when said switch arm is suiciently flexed. The contact point 38 iscarried by a screw 3B which is threaded through a block 4D of insulationmaterial carried by brackets 4I "secured to the inner face of the baseI6. The screw 39 may be turned to adjust the normal gap between thecontact points 31 and 38, so as to regulate `the temperature at whichthe pilot switch will close. A lock nut 42 serves to hold the contactpoint 38 at the desired adjustment.

The base I6 carries a pair of terminal pins or prongs 43 and 44respectively, adapted to engage sockets in a plug through which thecurrent is admitted to the apparatus. As shown in Fig. 4, the terminal43 is connected by a line 45 to one end of the main resistance unit I8.The other end of said resistance unit is connected to a xed Contactpoint 46 of the main switch. The op posed contact point 41 movable bythe switch handle 25, is connected by a wire 48 to the terminal 44. Thepilot switch point 38 is connected to the line 45, while the switchpoint 31 is grounded through the switch arm 35 to the percolator. Theheating coil 35 is connected at one end to the main switch point 4B,while the other end is grounded to the percolator.

The operation of 'the device is as follows: Cul rent is turned on to themain resistance unit I8 by throwing the switch handle 26 thereby flexingthe actuator 3|. However, no current passes through the heating coil 35because the ground is .not connected to power. In due course,temperature of the water in the receptacle l5 will rise to apredetermined degree sufficient to flex the pilot switch and close thecontacts 31 and 3B. This will energize the ground and con sequentlycurrent will flow through the heating coil 35 in parallel with theresistance unit it. The actuator when heated sufficiently will pull themain switch open, thereby decnergizing the resistance unit I8 and alsothe heating coil 35. The heating coil 35 is preferably so wound that apredetermined time interval will take place after the pilot switch hasbeen closed before the actuator will develop sufficient power to openthe main switch. It will be observed that the f take place until thetemperature in the receptacle I5 has been lowered, the current willalready have been cut orf from the coil 35 and there will be no sparkingacross the Contact points 31 and 38.

The construction just described is particularly applicable to apparatuswhere the actuator is not subjected to a high temperature. As ex plainedabove, the percolator shown in Fig. l is of the type in which thepumping is effected by local heating and the entire body of liquid inthe receptacle I5 is not brought to a high temperature until about thetime that it is desired to cut off the current. In other forms ofpercolaters where the entire body of liquid in the main receptacle mustbe brought up close to the boiling temperature before the percolatingstarts, it is desirable to use a construction in which the main switchand actuator are not built into the apparatus, and in which the pilotswitch is locatedv outside the apparatus so as to retard the heatingthereof. The same applies to other apparatus besides percolators and toillustrate my invention, I have shown such a construction adapted to beused on a flat iron.

As shown in Fig. 5, a pilot switch is mounted on the outside of the iron50. The switch comprises a strip of thermostatic metal 5I carrying acontact point 52 which is adapted to engage a contact point 53 when adesired temperature has been reached. The contact point 53 is insulatedfrom the main body of the iron 5Il` and is connected to one of theprongs 54 of the plug switch. These prongs project from a socket casing55 adapted to receive a connection plug 56. The `construction of theplug is shown in Fig. 6 and is or a type embodying a switch controlledby a material 60 to a feed wire 6I while the other is connected to aswitch blade 62. The latter may be swung into and out .of engagementwith a contact plate 63 connected to the other feed wire 64. 'I'he blade62 is pivoted at 65 to the casing of the plug, and a spring 66 isconnected at one end to the outer end of the blade 62 and at the otherend to the push bar 51 at the point 61. By moving the bar 51, the point61 is carried to one side or the other of the pivot 65, thereby causingthe blade 62 to snap into "on and off position. Within the plug casing,I provide a thermostatic actuator 68 which is of the same rtype as thatshown at 3| in Fig. 3. One end of this actuator is iixed to the casing,while the other end bears against a pin 69 on one end of a lever 10. Theother end of the lever engages a pin 12 ,on the rod 51. Surrounding theactuator 68 is a heating coil 13. Surrounding the socket portion'of theplug is a band 14 of conducting material which is adapted to engage thecasing 55 when the plug is applied to the iron.

'I'he operation of the apparatus will be understood by referring to thediagram of connections in Fig. 7. The heating unit of the iron is shownat 15 and is connected to the prongs 54 in the usual manner. When thebar 51 is pushed to the position shown in Fig. 6, the switch in the plugis closed and current ilows through the heating unit 15. When in thisposition, the actuator 68 is ilexed. The heating coll for the actuatoris connected at o'ne `end. by a wire 16 to the band 14 so that when theplug is inserted in the casing 55 one end of the heating coil isconnected to the actuator itself, and the latter is connected to thecontact member 63. When the iron has been heated to a predeterminedtemperature the pilot switch 5| will be flexed, closing the contactpoints 52 and 53. This will energize the ground, so that current willnow ilow through the coil 13, heating the actuator until the latteroperates to throw the switch to oiI position. Current is thereby cfutoif from the coil 13 as well as from the main resistance unit 15. In duecourse of time when the iron is cooled sufficiently, the pilot switchwill open, but there will be no current flowing through the switch atthe time, and consequently there will be no sparking between the contactpoints 52 and 53.

Obviously it is essential that the plug be inserted in the socket casing55 right side out else the heating coil 13 will not be energized whenthe pilot switch is closed. To this end I provide a pin 16v on the plug`and a slot 11 in the casing 55 adapted to receive the pin when the plugis inserted right side out. The pin, however, serves as a stop toprevent improper insertion of the plus.

In Fig. 8, I show my automatic switch mechanism applied to a wallieiron. The wallie iron is of the type having an indicating lamp 18 at thetop which lightsr up when'the iron has been heated to requisitetemperature. In this apparatus, the switch me anism is similar ingeneral construction to th'a shown in Fig. 1 with a main switch of thetoggle type in thebase of the iron, the handle of which switch is shownat 26, and also a pilot switch 36 in the base oi' the iron. 'I'he lamp18 is connected to the circuit, as shown by broken lines in Fig. 4. Oneend oi lthe lamp is connected to ground and the other to switch point46. When the current is applied, the lamp 18 as well as the heating coilwill bedead, but as soon as the temperature has risen tovsuch a pointvas to close the pilot switch the ground will be- 3 energized throughsaid pilot switch and this will cause the lamp and the coil 35 to beenergized.

When the lamp is light -i, the operator will knowthat sui'cientterfipf'ure has been reached either to place the batter in the wallieiron, or to remove a baked cake from the waie iron and at the same timethe current is turned oil automatically when, or shortly after, thiscondition is reached, the interval between the closing of the pilotswitch and opening of the main switch depending upon the capacity of theresistance unit 35.

Under some conditions, it is desirable to have the current turned on aswell as off under thermostatic control and to this end, I provide theconstruction shown in Fig. 9. In said iigure, I show a main switch 80 ofthe mercury type. The bulb of the switch is provided with a central band8| formed with trunnion pins 82 which are journaled in a yoke 83. One ofthe trunnion pins has a bifurcated arm 84 iixed thereon. An actuator 85,similar in form to the actuators 68 and 3 I. is fixed at one end to asuitable support 86 while the other end projects between the furcationsof the arm 84. A heating coil 81 is provided for the actuator. Theelectrical connections for the switch of this type are similar to thoseshown in Fig. 5. The arrangement is such that the switch is normally'inthe on Aposition supplying current to a main resistance .unit 90. When apredetermined degree of temperature is. reached, a pilot switch- 9|closes, thereby connecting the heating coil 81 in parallel with theresistance unit 90. When the actuator is flexed by heat generated by thecoil 81, the main switch is oscillated to oi position, thereby cuttingoff current from the heating coil 81 as well as from the main resistanceunit 90 of the apparatus. When the apparatus has cooled suiilciently forthe pilot switch 9| to break the circuit through the coll 81, theactuator will turn the switch 80 back to on" position. By this means, itis possible to maintain the apparatus between fixed limits oftemperature, with the Acurrent being turned on and oi by the actuatorunder control of the pilot switch.

In Fig. 10, I show a mercuryswitch in a connection plug withthermostatic means for turning the current on and oil". The constructionis similar to that shown ,in Fig. 6, except that in place of themanually controlled switch, a mercury lbulb switch 93 is used. 'Ihemercury bulb is provided with an encircling band of metal S4 formed withtrunnion pins which `are journaled in brackets 95. This plug is adaptedto be used in horizontal position, and consequently, the axis of thetrunnions is parallel to, or coincides with the longitudinal axis of theplug, so that the bulb will oscillate transversely with respect to theplug. Projecting from the upper side of the band 94 are a pair of pins96 between which extends one end of a thermostatic actuator 91. Thelopposite end of the actuatoris fixed to a bracket 98 secured to theplug'. About the actuator is wound a heating coil 99. 'I'he plug isprovided 65 with a band oi.' metal |00 at its forward or socket end.v Alead wire |01 connects with `the usual spring contact |02 in one of thesockets of the plug and the other lead wire |03 runs to a terminal |04.This terminal is connected to one of the contact points |05 of themercury bulb and the otherA contact |06 is connected to the other springcontact |01 in the other plug socket. The heating coil 89 is connectedat one `end to the actuator 91 and the latter is connected by a YwireY|08 to 75 the terminal |04. The other end of the heating coil 99 isconnected by a lead |09 to the band |00.

The operation of this plug switch will be readily apparent. The plugmust be inserted in horizontal position into the apparatus which isprovided with a pilot switch such as that shown on the at iron in Fig.5. The mercury bulb is normally in on position and when a predeterminedtemperature is reached in the apparatus to which the plug is applied,the heating coil S9 will be energized by the closing of the pilot switchand this will cause the actuator to swing the bulb to off position. Whenthe apparatus cools below said temperature the heating coil 99 will bedeenerglzed and the actuator will cool oi returning the bulb to onposition. There will be a lag between the on and off position while theactuator is cooling and this lag may be controlled by proper design ofthe apparatus.

The construction shown in Fig. 1l is very similar to that shown in Fig.10. The main dif ference is that the plug of Fig. 11 is adapted to beused in a vertical position, or in a position at a decided angle fromthe horizontal. The main dierence between the two' structures is' thefact that the mercury bulb is mounted to oscillate on an axis which isnormal to the longitudinal axis of the plug. In Fig. 41l., the samereference numerals are used as in Fig. 10 toindicate correspendingparts. Instead of the two brackets 95, a single double armed bracket 95is used, the two arms extending on opposite sides of the bulb andproviding bearing for the trunnion pins. The actuator S1 is somewhatshorter than the actuator 91 and the end of said actuator plays betweenthe pins 9B projecting from the band 94. The operation of this plugswitch is exactly the same as that shown in Fig. 10, except as to direcntion of oscillation of the mercury bulb.

Obviously, my automatic switch may be adapted i'or a wide variety ofapplications and its use is not limited to the particular apparatuschosen for illustration. I also reserve the right to make such changesin form, construction and arrangements of parts as fall within thespirit and scope of the following claims.

I claim:

1. The combination with an electric two position snap switch, of asingle manual means for throwing the switch to either of its twopositions and a thermostat having a link connection with said switch andincluding a bimetal member adapted when heated to warp and thereby movethe switch from one of its positions to its other position but when coldto yield to movement of the switch. to either position.

2. The combination with an electric two posi tion snap switch, of asingle manual means for throwing the switch to either on or off positionand a thermostat having a link connection therewith to move said switchfrom its on position to its oi position when the thermostat is heatedand to thereafter return to position permitting either manually on oroff position of said snap switch by movement of said single manual meanswhen said thermostat is cold.

3. The combination with an electric two position snap switch including aspring, oi a manualiy operable element for moving the switch 'towardeither of its two positions, said spring effecting completion of suchmovement to either of said 25 positions and a thermostat connected withsaid switch and including a bimetal member adapted when heated to warpand thereby move the switch from one of its positions to position wheresaid spring can complete the movement ot said switch 30 to its otherposition but when cold to yield to movement of the switch to eitherposition.

4. The combination with an electric two position snap switch including aspring, of a manually operable element for .moving the switch toward 35either on or oit position, said spring eiiecting completion of suchmovement to either of said positions and a thermostat connectedtherewith to move said switch from its on position to posiIm tion wheresaid spring can complete the movement of said switch to its off positionwhen the thermostat is heated and to thereafter return to positionpermitting either manually on or off posie tion of said snap switch bymovement of said single manual means when said thermostat is cold.

JGHN E. SMITH.

